/Engine/Plugins/Importers/USDImporter/Source/UnrealUSDWrapper/Public/UnrealUSDWrapper.h
These are the extensions for the file formats built into USD (i.e. "usd", "usda", "usdc", and "usdz").
static [TArray](API\Runtime\Core\Containers\TArray)< [FString](API\Runtime\Core\Containers\FString) > GetNativeFileFormats()